首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1380592篇
  免费   117680篇
  国内免费   6472篇
耳鼻咽喉   17268篇
儿科学   44207篇
妇产科学   37430篇
基础医学   189529篇
口腔科学   37248篇
临床医学   124982篇
内科学   288327篇
皮肤病学   32710篇
神经病学   114755篇
特种医学   57189篇
外国民族医学   275篇
外科学   217331篇
综合类   31870篇
现状与发展   2篇
一般理论   451篇
预防医学   109633篇
眼科学   28786篇
药学   96306篇
  5篇
中国医学   2271篇
肿瘤学   74169篇
  2018年   14515篇
  2017年   11404篇
  2016年   13625篇
  2015年   15259篇
  2014年   21350篇
  2013年   31738篇
  2012年   39205篇
  2011年   42012篇
  2010年   26127篇
  2009年   25596篇
  2008年   39169篇
  2007年   41721篇
  2006年   42666篇
  2005年   41238篇
  2004年   39164篇
  2003年   38161篇
  2002年   35991篇
  2001年   66665篇
  2000年   68546篇
  1999年   57166篇
  1998年   17228篇
  1997年   15406篇
  1996年   16328篇
  1995年   16547篇
  1994年   15379篇
  1993年   14431篇
  1992年   47493篇
  1991年   46166篇
  1990年   44317篇
  1989年   42143篇
  1988年   39083篇
  1987年   38420篇
  1986年   36186篇
  1985年   34974篇
  1984年   26703篇
  1983年   22370篇
  1982年   14047篇
  1981年   12634篇
  1980年   11924篇
  1979年   23771篇
  1978年   17266篇
  1977年   14547篇
  1976年   13341篇
  1975年   13869篇
  1974年   16286篇
  1973年   15582篇
  1972年   14323篇
  1971年   13168篇
  1970年   11979篇
  1969年   11214篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Pigeons were trained to peck a red or green center key 15 times to turn it off. After a delay, two side keys, one red and one green were illuminated. Pecks on the side key whose color matched the color that the center key had been produced food. Pecks on the other side key produced a timeout. The effects of various drugs were studied as the delay between extinguishing of the center key light and illumination of side keys was varied from 1 to 8 sec. Pentobarbital and phencyclidine consistently decreased matching, but morphine, d-amphetamine and delta 9-tetrahydrocannabinol had little effect on matching even at doses that increased latency to respond and decreased the rate of responding. Pentobarbital frequently decreased matching at doses below those that increased response latency and decreased response rate, but phencyclidine decreased matching only at doses that increased latencies and decreased rates. The effects of pentobarbital on matching did not depend on the delay duration.  相似文献   
992.
993.
Hallux rigidus (osteoarthritis leading to reduced motion) is one of the most common afflictions of the first metatarsophalangeal joint. The diagnosis is based on the presence of pain, specific physical findings, and certain radiologic features. In this essay, we illustrate the grades of radiologic changes, which are an integral part of the surgeon's preoperative evaluation, and show examples of the postoperative radiologic appearance.  相似文献   
994.
Small intestinal transplantation represents a potentially therapeutic procedure for individuals with short gut syndrome. The purpose of this study was to develop a model for small intestinal transplantation in primates that is: technically feasible without microsurgery; consistent in the prevention of allograft rejection; functional in terms of nutrient absorption; and compatible with harvest for multiple organ procurement. First, autotransplantations on four rhesus monkeys were performed in order to study a variety of harvesting techniques and vascular anastomoses. Then, a study was performed with 14 heterotopic allotransplants in 4 baboons and 10 rhesus primates. The successful donor model consisted of division of the pancreas, harvesting the small bowel with a superior mesenteric artery and portal vein pedicle. The allograft vascular pedicle was anastomosed to the recipient's common iliac vessels in end-to-side fashion. The graft was transplanted as an out-of-continuity loop, both ends being exteriorized as stomas providing access for absorption studies and biopsy. Three immunosuppressive regimens were tested: (1) cyclosporine A (CyA) 20 mg/kg/d, solumedrol (SML) 2 mg/kg/d, and graft irradiation (150 rad) (n = 4); (2) CyA 20 mg/kg/d and SML 2 mg/kg/d (n = 3); and (3) CyA 40 mg/kg/d, SML 2 mg/kg/d, and azathioprine 5 mg/kg/d (n = 3). There were 4 deaths due to technical error in the first 24 hours. Weekly graft biopsy, serum CyA levels, complete blood count, and automated 24-channel serum analysis were performed. Grafts surviving greater than 14 days underwent absorption study via luminal perfusion with sucrose, maltose, dextrose, Pregestimil, xylose, and cyclosporine.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
995.
Non-epithelial neoplasms of the stomach are rare in all countries, in contrast to neoplasms of epithelial origin. They can be either benign or malignant. The distinction between these two groups is based entirely on histopathology. This paper reports a series of 27 patients managed during the period June 1978 to March 1991.  相似文献   
996.
997.
Creativity and problem solving are closely related in the learning and practice of nursing. The problem underlying this study concerns the attitudes of professors of nursing in 321 French language community colleges in Quebec toward the creative characteristics of their students. However, given the absence of a valid and reliable French instrument, this study focused on the validation of a French version of Torrance's Ideal Pupil Checklist. Content, construct and criteria validity were all verified, as well as the stability and homogeneity aspects of reliability.  相似文献   
998.
alpha 2-Adrenergic receptors (ARs) are involved in central nervous system (CNS) control of blood pressure. It is now known that there are three human genes that encode subtypes of alpha 2-ARs, but little is known regarding the distribution of these subtypes throughout the CNS. The availability of receptor clones allows the mapping of mRNAs encoding the individual alpha 2-AR subtypes in the CNS. In this communication, we report that there are three, closely related rat alpha 2-AR genes. We have developed subtype-specific hybridization probes from each of these genes and have used these reagents to measure alpha 2-AR subtype mRNA accumulation in extracts of discrete regions of the rat CNS. We found that mRNAs encoding the alpha 2A-AR and alpha 2C-AR subtypes are distributed widely, but unevenly, throughout the rat CNS. The A subtype is prominent in the midbrain, brainstem, spinal cord, pituitary and diencephalon while the C subtype predominates in basal ganglia and cerebellum. The cortex, olfactory bulb and hippocampus contain roughly equal amounts of the alpha 2A- and alpha 2C-AR mRNAs. A third subtype's (alpha 2B-AR) mRNA is far less abundant in brain tissues, and is only found in the diencephalon.  相似文献   
999.
1000.
We isolated cDNA clones from an Aplysia sensory-cell library encoding two isoforms of protein kinase C (PKC). Several isozyme-specific regions are conserved in the Aplysia kinases, notably the variable regions V5 in the Ca(2+)-dependent PKC (Apl I) and V1 in the Ca(2+)-independent PKC (Apl II). Neuronal proteins with the properties expected of these two isoforms can be identified with antibodies raised against peptides synthesized from the amino acid sequences deduced from the clones. Sacktor and Schwartz (1990) measured the proportion of kinase activity that can be translocated to membrane in Aplysia sensory neurons and ganglia by stimuli that produce the presynaptic facilitation underlying behavioral sensitization. Much less Apl I and Apl II are translocated, suggesting that still other isoforms of PKC exist in these cells.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号